What was found
WHILE CLIMBING OUT OF FL390 THE CREW NOTICED A VIBRATION SHORTLY FOLLOWED BY A CYAN L ENG HYD PUMP FAIL EICAS MSG. THE CREW VERIFIED THE PUMP FAILURE ON THE HYDRAULIC SYNOPTIC PAGE. SOON AFTER A L HYD PRESS LOW CAS MSG WAS RECEIVED. THE FLIGHT CREW DECLARED AN EMERGENCY AND RETURNED TO KMRY. MX REPLACED LT HYDRAULIC ENGINE DRIVE PUMP EDP AND FLUSHED HYDRAULIC SYSTEM. PERFORMED OPS AND LEAK CHECKS. ACFT RETURNED TO SERVICE.